Abstract: Over 1,000,000 biopsies are performed annually in the United States to diagnose prostate cancer (PCa)[1]. Prostate biopsies are performed using transrectal ultrasound (TRUS) guidance to diagnose PCa when suspicion is raised through screening mechanisms. However, ultrasonic prostate imaging does not facilitate targeting biopsies to suspicious regions because PCa does not have unique B-mode image characteristics that can delineate diseased tissues from normal structures and benign pathologies. Therefore, the current standard of care has poor sensitivity mainly because the sampling grid, which samples <5% of the prostate, only randomly intersects pathologic tissues. As a result, PCa detection rates are only 18-36% for both ?rst and second-time repeat biopsies[1?5]. In addition, many of the cancers that are detected with the systematic sampling approach are clinically insigni?cant [2, 6], leading to overly aggressive treatment that adversely affects patients and places an unnecessary burden on our healthcare system. During the previous funding cycle we developed a novel 3D Acoustic Radiation Force Impulse (ARFI) prostate ultrasound elasticity imaging system. Our experience with 3D ARFI prostate imaging in over 100 patients demonstrated the exciting result that 3D ARFI imaging is speci?c for clinically signi?cant disease (CSD)[7], which means it can be used to screen the entire prostate gland and target biopsies toward regions suspicious for CSD. We have identi?ed the key technical challenges that must be addressed to bring a low-cost, 3D-ARFI prostate cancer screening and targeted biopsy guidance system into the current clinical work-?ow. In this competing renewal, submitted under PAR- 15-075 for academic-industrial collaborations, we propose to partner with Siemens ultrasound to resolve these challenges and build a clinic-ready system and assess its performance in the clinic as compared to systematic TRUS biopsy. The proposed system will remove the random nature of systematic sampling, facilitating initial diagnosis based upon the most aggressive disease present in the gland. We hypothesize that this system will reduce the required number of biopsy cores, the number of repeat biopsy procedures, and the number of unnecessary radical prostatectomies associated with PCa. There are 3 speci?c aims: 1) To translate our prototype system into a clinic-ready system through: development and integration of a custom designed, side-?re transrectal transducer and biopsy needle guides, implementation of our data processing and 3D data visualization tools on-board a state-of-the-art prototype ultrasound scanner, and integration of positioning feedback in the motorized rotation system. 2) To assess the performance of the 3D TRUS ARFI targeted biopsy guidance system in tissue mimicking phantoms. 3) To assess the performance of 3D ARFI in vivo in humans in targeting clinically signi?cant prostate disease.